Paper-based sensing (i.e. paper based test devices) is an emerging technology that has advantages relative to traditional test strips in terms of cost and multiplexing. The concern of poor accuracy on paper-based sensors and paper test strips, due to the colorimetric measurement, has limited them from quantitative applications. In existing test strip applications, a user has to manually compare resultant colors to a set of colors on a reference card. This is neither user friendly nor reliable. Recently some companies have developed phone ‘apps’ to automate the test strip reading process using a phone camera.